If a patient has an unstable fracture of the ulna, which type of cast is appropriate?

In the case of an unstable fracture of the ulna, a long-arm cast is appropriate because it provides additional support and immobilization to the elbow joint, not just the wrist and forearm. The long-arm cast extends from the upper arm down to the wrist, ensuring that both the ulna and the surrounding structures are stabilized. This is crucial for fractures that are unstable, as they require more extensive immobilization to promote proper healing and to prevent complications such as malunion or nonunion.

A short-arm cast would not provide sufficient support for an unstable fracture, as it only covers the forearm and wrist without stabilizing the elbow. Similarly, a thumb spica cast, which is typically used for injuries involving the thumb or wrist, would not offer the necessary support for a fracture of the ulna. Lastly, a hanging-arm cast is not a standard option for treating fractures and would not effectively immobilize the fracture site as needed. Therefore, the long-arm cast is the best choice for managing an unstable ulna fracture, providing comprehensive immobilization to facilitate proper healing.